Musannaf Ibn Abi Shayba 33:1301

Ibn al-Mubarak narrated to us, from al-Rabi’ ibn Anas, from Abu Dawud, from Ubayy ibn Ka’b, who said: "Adhere to the path and the Sunnah, for there is no servant who is upon a path and a Sunnah, and remembers the Most Merciful, and his eyes overflow with tears out of fear of Allah, but that the Fire will never touch him. And there is no servant who is upon a path and a Sunnah, and remembers Allah, and his skin shivers out of fear of Allah, but that he is like a tree whose leaves have dried; it is like that, when a wind hits it, its leaves fall off from it, except that his sins fall off just as the leaves fall off from this tree. And indeed, moderation in a Sunnah and a path is better than exertion in other than a Sunnah and a path. So look at your deeds; for if they are [in] moderation and exertion, let them be upon the methodology of the Prophets and their Sunnah."